All the current is again blocked by the transistor and we get low voltage at the output, which turns OFF the LED.įig. Commonly classified into Bipolar Junction Transistors (BJT), and Field Effect Transistors (FET), these devices allow for the existence of radios, computers, calculators. 2: Circuit Diagram of Transistor based OR Gate How It Works The transistors are connected in parallel and their bases are used as input. It is just enough to make LED B glow dimly. When the switch is closed a small current flows into the base (B) of the transistor. The small base current controls the larger collector current. The base to emitter junction and base to collector junction of both the transistors have a voltage lower than the threshold voltage and again they reach their cutoff state. A transistor is defined as a semiconductor device that’s fundamentally built with three terminals for amplifying or switching electronic signals and electrical power purposes. The diagram shows the two current paths through a transistor. As the second transistor is still in its cutoff state, the emitter of the first transistor is disconnected. In next case when we press switch 1 then the base of the first transistor gets a positive value of voltage but its emitter is connected to another transistor collector. Hence at the output, we get a low voltage which turns off the LED. Since all the current coming from the collector through resistor R3 blocks by the transistor. Now you will apply it and build your own simple amplifier circuit from scratch using two transistors and some various resistors/capacitors. Therefore, the transistors act like an open switch. The base to emitter junction and base to collector junction of both the transistors have a voltage lower than 0.65V, which is the practical threshold voltage of the diode.īoth junctions are in reverse bias hence both the transistors turn off and go into their cutoff state. Initially, both the switches are in OFF state so none of the transistor bases get a power supply. The base of both the transistors act like inputs and one of the emitter of either of the transistors is used to derive the output. Since their invention in 1947, transistors have been used in electronic devices all over the world. The transistors are connected in series and their bases are used as input. An NPN transistor pinout is a type of diagram explaining the terminals attached to the device.
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